A total of 68 aquatic beetles were recorded from Sata Pond, the dew pond and Reservoir Pond - a very respectable total for any site. These included several scarce or localised species (Appendix III).
Of special note is the whirligig beetle Gyrinus distinctus (two collected from the Reservoir Pond), a 'Red Data' species associated with lakes or large ponds fringed by tall marginal vegetation.
Species listed as Nationally Scarce (Nationally Scarce species are believed to occur in fewer than 100 ten squares in Britain) include:
Hydroporus obsoletus - a small diving beetle associated with springs; a single specimen was collected from Sata Pond on 25th June. There are a handful of Yorkshire records with this being the only recorded locality in Ryedale.
llybius fenestratus - a widespread but local, bronzey-coloured diving beetle which is numerous in the Reservoir Pond. This beetle secretes a powerful cocktail of steroidal chemicals which deters predators, enabling it to survive in water bodies stocked with fish. It is known from two other lakes in the Howardian Hills.
Other uncommon species include:
Agabus affinis - a very local diving beetle associated with mossy fens and mires, found in Sata Pond along with the closely-related A. unguicularis.
Agabus unguicularis - a very local diving beetle found in richly-vegetated ponds; known from only two other localities in Ryedale.
llybius guttiger - a medium-sized black diving beetle found in mossy fens and mires and only known from a handful of Yorkshire localities, most of which are 'ancient' wetlands. Numerous in shallow water amongst beds of bottle sedge in Sata Pond.
Rhantus exsoletus - a mottled brown and orange diving beetle found in the richly-vegetated margins of the Reservoir Pond, mainly amongst sedge beds. Only known from a small number of Yorkshire sites.
Dytiscus semisulcatus - a very large, jet black diving beetle recorded from Sata Pond and the dew pond. This species is rare in Yorkshire but there are large populations on Strensall Common. Its larvae are specialist predators on caddis grubs.
Cercyon ustulatus-a rounded scavenger water beetle found in pond margins; very local.
The presence of four types of reed beetle is notable, although all of those recorded here are fairly common. These are striking, metallic-coloured beetles which develop as larvae among the roots of aquatic plants; the adults feed on the aerial leaves of plants such as reedmace and sedges (Donacia versicolorea feeds on the floating leaves of broad-leaved pondweed).
The mossy fen at Sata Pond is also rich in rove beetles and ground beetles, although these were not studied in any detail. The Green Tiger Beetle (Cicindela campestris), a localised species of dry, heathy habitats, was observed around the Sand Pit. |
